Cfrgtkky

I'm using the following packages:

usepackage{mathrsfs}

usepackage{mathtools}

usepackage{amsmath,latexsym}

in order to write the following equation.

begin{eqnarray*}

frac{partialmathscr{L}}{partial(partial_nu A_mu)} =-frac{1}{4} left[ 

left(frac{partial(partial_sigma A_omega)}{partial(partial_nu A_mu)}

 -frac{partial(partial_omega A_sigma)}{partial(partial_nu A_mu)}right)

(partial_alpha A_beta-partial_beta A_alpha) 

 + (partial_sigma A_omega - partial_omega A_sigma)

left(frac{partial(partial_alpha A_beta)}{partial(partial_nu A_mu)}

 -frac{partial(partial_beta A_alpha)}{partial(delta_nu A_mu)}right) 

right]

end{eqnarray*}

The problem is that the equation is too long for a single line. When I try to break it on the "plus" sign, it no longer recognizes the last right] command, and my brackets do not close. I Checked the code several times, it seems correct.

Any Ideas?

For the sake of completeness I'd like to suggest an automated solution using breqn. It can break a display math equation respecting left and right delimiters. An example without any change inside the formula:

documentclass{article}

usepackage{amsmath}

usepackage{mathrsfs}

usepackage{breqn}

begin{document}

begin{dmath*}

frac{partialmathscr{L}}{partial(partial_nu A_mu)}

  =-frac{1}{4}left[left(

      frac{partial(partial_sigma A_omega)}{partial(partial_nu A_mu)}

      -frac{partial(partial_omega A_sigma)}{partial(partial_nu A_mu)}right)

      (partial_alpha A_beta-partial_beta A_alpha) 

      + (partial_sigma A_omega - partial_omega A_sigma)

      left(frac{partial(partial_alpha A_beta)}{partial(partial_nu A_mu)}

        -frac{partial(partial_beta A_alpha)}{partial(delta_nu A_mu)}

      right)right]

end{dmath*}

end{document}

The result mimics multline:

it seems that for your long equation is multlined appropriate math environment:

documentclass{article}

usepackage{mathrsfs}

usepackage{mathtools, amssymb}



%---------------- show page layout. don't use in a real document!

usepackage{showframe}

renewcommandShowFrameLinethickness{0.15pt}

renewcommand*ShowFrameColor{color{red}}

%---------------------------------------------------------------%



begin{document}

    begin{multline*}

frac{partialmathscr{L}}{partial(partial_nu A_mu)}

    = -frac{1}{4} left[left(

            frac{partial(partial_sigma A_omega)}

                 {partial(partial_nu A_mu)}

          - frac{partial(partial_omega A_sigma)}

                 {partial(partial_nu A_mu)}right)right.

           (partial_alpha A_beta-partial_beta A_alpha)        \

      + (partial_sigma A_omega - partial_omega A_sigma)

        left.left(

            frac{partial(partial_alpha A_beta)}

                 {partial(partial_nu A_mu)}

          - frac{partial(partial_beta A_alpha)}

                 {partial(delta_nu A_mu)}right)right]

    end{multline*}

end{document}

(red lines indicate text borders)

You wrote,

I Checked the code several times, it seems correct.

Actually, it is not correct: TeX syntax rules do not allow line breaks inside a left[...right] group. The solution is not to use left and right to begin with. Instead, do use biggl[ and biggr].

Here's a solution which uses an align* environment -- please don't use the badly deprecated eqnarray* environment -- and rearranges the multiplicative terms in the second row so that than can be aligned with the corresponding terms in the first row. And, all auto-sizing directives have been replaced with the explicit-sizing instructions biggl and biggr.

documentclass{article}

usepackage{mathrsfs}  % for 'mathscr' macro

usepackage{mathtools}

usepackage{%amsmath, % is loaded automatically by 'mathtools' package

            amssymb}   % not 'latexsym'!



begin{document}



begin{align*}

frac{partialmathscr{L}}{partial(partial_nu A_mu)}

=-frac{1}{4} biggl[ 

&biggl(frac{partial(partial_sigma A_omega)}{partial(partial_nu A_mu)}

-frac{partial(partial_omega A_sigma)}{partial(partial_nu A_mu)}biggr)

(partial_alpha A_beta-partial_beta A_alpha)\

{}+{} % make '+' act like a binary, not unary, operator

&biggl(frac{partial(partial_alpha A_beta)}{partial(partial_nu A_mu)}

-frac{partial(partial_beta A_alpha)}{partial(delta_nu A_mu)}biggr)

(partial_sigma A_omega - partial_omega A_sigma) 

biggr]

end{align*}

end{document}